1. Field of the Invention
The present invention relates to a liquid ejecting head discharging a liquid from discharge port and a liquid ejecting apparatus mounting the liquid ejecting head.
2. Description of the Related Art
A liquid ejecting (ink jet) apparatus is of the so-called non-impact recording type, and has features of permitting recording of information at a high speed and on various recording media, and of being almost free from noise upon recording. On account of these features, the liquid ejecting apparatus is widely adopted as a recording apparatus in printers, wordprocessors, facsimile machines, copying machines and the like.
The liquid ejecting apparatus is based on steps of discharging fine liquid drops from small discharge ports arranged on a liquid ejecting head and depositing these drops onto a recording medium, thereby accomplishing recording. Discharge energy generating elements using a piezo-element or an electro-thermal conversion element are known. Such a liquid ejecting apparatus generally comprises a liquid ejecting head having a nozzle for forming liquid drops, and a liquid feed system feeding the liquid to the liquid ejecting head. For example, in a liquid ejecting head using an electro-thermal conversion element, heat energy is imparted to a liquid by providing the electro-thermal conversion element in a nozzle and applying electric pulses giving a discharge signal thereto, and a foaming pressure occurring upon foaming (boiling) of the liquid caused by a phase change of the liquid is used for discharging liquid drops.
Liquid ejecting heads using electro-thermal conversion as described above are classified into a type in which the liquid is discharged in parallel with an element board having electro-thermal conversion elements arranged thereon (edge shooter), and a type in which the liquid is discharged perpendicularly to the element board having electro-thermal conversion elements arranged thereon (side shooter). A concrete configuration of the liquid ejecting head will now be described by citing the side shooter as an example with reference to FIGS. 15 and 16.
FIG. 15 is a schematic perspective view of a liquid ejecting head of a conventional side shooter; and FIG. 16 is a sectional view of the same liquid ejecting head cut along a direction (line Yxe2x80x94Y) perpendicular to the discharge port arranging direction.
In FIGS. 15 and 16, a plurality of discharge ports 202 for discharging a liquid are pierced on the surface side near the center of an element board 201, and electro-thermal conversion elements (called also heating elements or heaters, and hereinafter simply referred to as heating elements) 203 corresponding to the individual discharge ports 202, for heating the liquid are formed on the element board 201.
Electric wiring of the heating elements 203 is connected to a transistor circuit for driving the heating elements 203. The transistor circuit is built in the element board, or mounted by mounting a separate element having a built-in transistor circuit. In an element board having a relatively small number of heating elements, it is the usual practice to build a transistor circuit in the element board. In an element board having a relatively large number of heating elements for the purpose of increasing the printing width, the configuration having the transistor circuit built in the element board leads to a considerable decrease in yield of the element board. The method of mounting the separate element having the transistor circuit built therein onto the element board is more advantageous in yield. FIGS. 15 and 16 illustrate a conventional case where separate driving elements (drivers IC) 205 having built-in transistor circuit for driving the heating elements 203 are mounted on the element board 201.
The driving element 205 having the transistor circuit for driving the heating element 203 is mounted on the element board 201 by the COB (chip on board) connecting method using an anisotropic conductive film or a soldered bump, and electrically connected to the electric wiring from the heating element 203. A logic circuit for driving the transistor is mounted on the driving element 205, in addition to the transistor circuit. The logic circuit is connected to a flexible film (flexible circuit board) 206 via the element board 201, and a signal for driving the logic circuit is provided via the flexible film 206. The flexible film 206 is connected by the COB connecting method based on an anisotropic conductive film or the like to a circuit board 207 comprising a composite material of the element board 201 and a glass epoxy or the like. The circuit board 207 is fixed to a side of a supporting member 212 and electrically connected to an area outside of the head. The flexible film 206 is bent along the side surface of the supporting member 212 from an end of the element board 201.
The electric connecting portions of the driving element 205 and the flexible film 206 are covered and sealed by a sealing agent 214 (FIG. 16) excellent in sealing and ion shielding abilities such as an epoxy resin, a fluororesin, or a silicone resin to avoid corrosion of electrodes or substrate metals caused by deposition on the electrodes of liquid drops scattering from the discharge port or liquid rebounding from the recording medium.
As shown in FIG. 16, a slit 204 for receiving the liquid fed from the back is formed by anisotropic etching or the like on the element board 201. Common liquid chamber 210 communicating with a slit 204 formed in the element board 201 are formed on a holding member 211 and the supporting member 212 of the element board. A liquid feed port 213 for feeding the liquid to the common liquid chamber 210 is formed in the supporting member 212. The liquid feed port 213 communicates with a liquid feed tank not shown. A liquid feed channel is formed by laminating the element board 201, the holding member 211 and the supporting member 212 as shown in FIG. 16.
In the liquid ejecting apparatus, when mixture of bubbles or dust in the fine discharge port (nozzle) 202 of the liquid ejecting head occurs, or when evaporation of volatile matter in the liquid prevents discharge of the liquid, a discharge recovery operation is conducted, in which factors causing defective discharge are eliminated by refreshing the liquid. Available methods for such a discharge recovery operation include a method of providing a cap capable of covering the discharge port of the liquid ejecting head and a pump communicating with this cap and applying a suction force, and forcibly sucking out the liquid from the discharge port under the action of the suction force in a state in which the liquid ejecting head and the cap are kept in close contact; and a method of providing a mechanism applying a pressure on the liquid from the liquid feeding side of the liquid ejecting head, and forcibly extruding the liquid from the discharge port of the liquid ejecting head by applying the pressure from the liquid feeding side. In any of these methods, it is necessary to keep the liquid ejecting head and the cap in a perfectly enclosed state not permitting in-flow or out-flow of the liquid or air.
When the liquid ejecting head is in a standby state in which the liquid is not discharged, it is necessary to maintain the liquid ejecting head and the cap in close contact to prevent an increase in viscosity caused by evaporation of a liquid solvent or by solidification.
For this purpose, in the liquid ejecting head, it is necessary to provide an area suitable for obtaining and maintaining close contact with the cap. In a conventional liquid ejecting head, a flat surface for receiving the cap 217 (see FIG. 16) is provided between the row of discharge ports on the element board 201 and the driving element 205.
However, in the conventional liquid ejecting head as described above, in which the flat area for receiving the cap 217 is provided on the element board 201, the necessity to increase the area of the element board 201 leads to the need to increase the size of the liquid ejecting head. Usually, when preparing an element board, a plurality of element boards are cut from a substrate. Increase in size of an element board corresponds to a decrease in the number of board available from a substrate, thus resulting in a large increase in the unit cost per head.
In the conventional liquid ejecting head with a printing width of up to 25.4 mm (1 inch), it is possible to build in functions of the driving element 205 in the element board 201. With a printing width having a length in the discharge port arrangement direction of over 25.4 mm (1 inch), there occurs an extreme decrease in the yield of integrated circuits. It is therefore inevitable to adopt the method of separately preparing driving elements 205 and mounting them on the element board 201 as described above.
Thus, because of the necessity to provide a flat area for receiving the cap 217 and an area for mounting the driving elements 205, the element board 201 must be larger in size, resulting in a wider width of the liquid ejecting head. When arranging a plurality of element boards widening the width of the liquid ejecting head also in the discharge port arrangement direction, there is an increase in the area where an appropriate gap is to be provided between the head and the recording medium to maintain a high print quality, so that it is easy to keep a certain gap over the entire area. Parallel arrangement of a plurality of liquid ejecting heads led to an increase in the size of the main body of the liquid ejecting apparatus, and hence to a cost increase.
Therefore, the present invention was developed in view of the aforementioned problems of the conventional art not as yet solved, and has as an object to provide a liquid ejecting head and a liquid ejecting apparatus which permits downsizing of the liquid ejecting head and cost reduction, and furthermore, to provide a liquid ejecting head and a liquid ejecting apparatus which permits size reduction of the liquid ejecting head, improvement of reliability of the electrical mounting section, and cost reduction.
To achieve the above-mentioned object, the liquid ejecting head of the present invention comprises a discharge port forming member having a plurality of discharge ports for discharging a liquid arranged therein; an element board having a plurality of discharge energy generating elements for imparting discharge energy to the liquid provided to face the plurality of discharge ports, respectively, and a liquid feed port communicating with the plurality of discharge ports; a holding member forming a common liquid chamber for feeding the liquid to the plurality of discharge ports via the liquid feed port of the element board and holding and fixing the element board; and a plurality of driving elements for driving the plurality of discharge energy generating elements; wherein the plurality of driving elements are mounted in a mounting area which is a region outside the discharge port forming member; and wherein the liquid ejecting head has a cap receiving member for capping the liquid discharge head in the mounting area, and the cap receiving member has a shape enclosing the discharge port forming member.
In the liquid ejecting head of the invention, the cap receiving member or a portion thereof should preferably be arranged on the plurality of driving elements. In this case, it is desirable that a complementary member or a sealing agent having substantially the same thickness as that of the driving element is arranged in an area where the driving elements are not mounted within the mounting area. Or, it is desirable that a portion of the cap receiving member arranged in the area not having the driving elements mounted thereon has a thickness larger than the portion having the driving elements mounted thereon, by the thickness of the driving element.
In the liquid ejecting head of the invention, a flexible circuit board for electrically connecting the plurality of driving elements to an area outside of the head is connected to the mounting area of the element board, and the cap receiving member is arranged also on the connecting portion of the flexible circuit board to the element board. In this case, a complementary member or a sealing agent having substantially the same thickness as that of the flexible circuit board is arranged in an area where the flexible circuit board is not arranged within the mounting area. Or, the portion of the cap receiving member arranged in the area not having the flexible circuit board arranged therein has a thickness larger than the portion having the flexible circuit board arranged therein by the thickness of the flexible circuit board. In the liquid ejecting head of the invention, the cap receiving member should preferably comprise a film material.
The liquid ejecting head of the invention comprises a discharge port forming member having a plurality of discharge ports for discharging a liquid arranged therein; an element board having a plurality of discharge energy generating elements for imparting discharge energy to the liquid provided to face the plurality of discharge ports, respectively, and a liquid feed groove communicating with the plurality of discharge ports; a holding member forming a common liquid chamber for feeding the liquid to the discharge ports via the liquid feed port of the element board and holding the element board; a plurality of driving elements for driving the plurality of discharge energy generating elements; and a flexible circuit board for electrically connecting the plurality of driving elements to an area outside of the head; wherein the driving elements are mounted on the element board, and the flexible circuit board is connected to the element board and bent substantially at a right angle at an end of the element board; and wherein the liquid ejecting head has a cap receiving member for receiving a cap for capping the liquid ejecting head around the element board; and the cap receiving member has a shape enclosing the discharge port forming member.
In the liquid ejecting head of the invention, the flexible circuit board should preferably be bent and inserted into a gap between the cap receiving member and the element board. In this case, it is desirable that at least a portion of the flexible circuit board corresponding to a side of the element board is covered with a protecting member fixed to the holding member, and at least a part of the cap receiving member is arranged on the protecting member. It is also desirable that a sealing agent is charged into a gap between the cap receiving member and the element board. The portion of the flexible circuit board arranged on the element board should preferably be covered with a sealing agent. The liquid ejecting head of the invention comprises a plurality of discharge port forming members having a plurality of discharge ports for discharging a liquid arranged therein; a plurality of element boards having a plurality of discharge energy generating elements for imparting discharge energy to the liquid provided to face the plurality of discharge ports, respectively, and a liquid feed port communicating with the plurality of discharge ports; a holding member forming a common liquid chamber for feeding the liquid to the plurality of discharge ports via the liquid feed ports of the plurality of element boards and holding and fixing the element boards; and a plurality of driving elements for driving the plurality of discharge energy generating elements; wherein the plurality of driving elements are mounted in a mounting area which is a region outside the discharge port forming members; and wherein the liquid ejecting head has a cap receiving member receiving a cap for capping the liquid discharge head in the mounting area, and the cap receiving member has a shape enclosing the discharge port forming member.
The invention provides also a liquid ejecting head comprising a plurality of discharge port forming members having a plurality of discharge ports for discharging a liquid arranged therein; a plurality of element boards having a plurality of discharge energy generating elements for imparting discharge energy to the liquid provided to face the plurality of discharge ports, and liquid feed ports communicating with the plurality of discharge ports; a holding member forming a common liquid chamber for feeding the liquid to the discharge ports via the liquid feed ports of the plurality of element boards and holding and fixing the element boards; a plurality of driving elements for driving the plurality of discharge energy generating elements; and a plurality of flexible circuit boards for electrically connecting the plurality of driving elements to an area outside of the head; wherein the plurality of driving elements are mounted on the element boards, and the flexible circuit board is connected to the plurality of element boards and bent substantially at a right angle at an end of each of said element boards; and wherein the liquid ejecting head has a cap receiving member for receiving a cap for capping the liquid ejecting head around the element board; and the cap receiving member has a shape enclosing in a lump the plurality of discharge port forming members.
In the liquid ejecting head of the invention, the discharge energy generating element may be a heating element which converts electric energy into heat energy and discharges the liquid accompanied by a foaming phenomenon of the liquid.
The liquid ejecting apparatus of the invention mounts the aforementioned liquid ejecting head and has a cap for capping the liquid ejecting head, wherein, when the liquid ejecting head is in standby state, capping is applied to the cap receiving member.
According to the present invention, in the liquid ejecting head, it is possible to reduce the area of the element board, to accomplish proper capping, and to avoid non-discharge at the start of liquid discharge without necessity of a special area for receiving the cap on the element board as in the conventional art. This is achieved by setting the portion for the cap in an area surrounding the row of discharge ports by use of the upper surface of the driving element mounted on the board element or the upper surface of the flexible film (flexible circuit board) connected to the element board, or on members arranged around the element board, so as to prevent evaporation of volatile constituents of the liquid. The ability to reduce the area of the element board permits cost reduction of the liquid ejecting head.
By adopting a configuration in which the flexible film extending from the mounting section on the element board is bent in the interior of the cap receiving member, or a configuration in which the flexible film is positioned on the lower surface of the cap receiving member, it is possible to protect the flexible film from the liquid by means of the cap receiving member, and to improve reliability by preventing exposure of the electric connecting sections to the liquid. Since the flexible film is not exposed to the conveying section of the recording medium, it is possible also to provide a liquid ejecting head free from damage to the flexible film caused by defective conveyance of the recording medium and therefore having a still higher reliability.
The liquid ejecting head itself can be downsized. When arranging the plurality of elements in parallel, it is possible to considerably reduce the area within which the interval between the head and the recording medium is controlled. This makes it possible to improve the print quality, reduce the size of the apparatus using a plurality of liquid ejecting heads, and to reduce the cost.
Further objects, features and advantages of the present invention will become apparent from the following description of the preferred embodiments with reference to the attached drawings.